The primary purpose of this investigation was to evaluate the relationship between chronic sinus symptoms and asthma in an occupational cohort. Secondary objectives were to investigate potential associations with other lower respiratory conditions or measures that also relate to obstructive processes of the lower airways. The design of the sinus question, in the form of a matrix, allowed the symptom to be classified as work-related or not. This lead to a set of analyses that enabled comparisons between work-related and non-work-related sinus symptoms. Various respiratory measures outcomes were studied for this purpose including: cross-shift change in-FEV1, percent predicted FEV1, FVC and PEF. Respiratory symptoms often associated with lower respiratory disease processes included measures of: bronchitis, chronic bronchitis, wheeze, cough, phlegm, shortness of breath, and chest tightness. Three upper respiratory symptoms, eye, nose and throat irritation were also evaluated in relation to chronic sinus symptoms. Because this was an occupationally exposed cohort, the relationship between chronic sinus symptoms and exposure was also evaluated using the following variables: duration of employment, machining versus non-machining, type of MWF (straight or soluble), mass aerosol concentration, operation type and part metal being machined. Cross-sectional data present some difficulties in terms of calculating rates of disease. This problem is even further complicated in studies of working populations because of selection pressures that result in the movement of workers away from jobs or exposures that are causing them discomfort or illness (healthy worker selection). Because cross-sectional data in effect, provide a snapshot of disease processes in a population, one has to make assumptions in terms of the timing of the relationship between exposure and disease. The picture is also likely to be somewhat inaccurate because some of the cases are no longer among the population or have changed their exposure status because of their discomfort or illness. These factors were problematic in these analyses when considering the relationship between asthma and sinus symptoms. Two separate approaches were used to address these problems. The first was based on the hypothesis that asthma which developed after employment in the plant was more likely to be related to exposure and therefore sinus symptoms than pre-employment asthma. The second approach (dichotomizing asthma cases into those diagnosed within the past 10 years versus more than 10 years ago) speaks more to the purported selection of asthmatics away from exposures that exacerbate or lead to their conditions. Although most of the post-hire asthmatics are contained in this group, the categorization further restricts the post hire asthmatics to those most recentlly diagnosed. This in effect should streamline the exposure-related cases and make the relationship between sinus symptoms and asthma even more visible or apparent.